Circuit boards, or devices containing large power supply bulk capacitance, experience an uncontrolled initial inrush current that charges the capacitance when power is initially applied. This inrush current can cause damage to components, system disruption or permanent failure thereof.
Recent tests have shown that various point-of-sale (POS) printers have inrush current that is not properly limited. Often, attempts to resolve the problem have been primitive, and have been only marginally successful. In addition, many of these previous attempts to deal with this problem have been expensive. It is not uncommon to experience disturbances or terminal resets when POS printers are connected to a POS terminal while it is powered up.
In some cases, an inrush transient may exceed thirty amperes, while the peak capacity of the supply is typically twelve amperes or less. An inrush circuit for a high-speed thermal POS receipt printer must present less than ten amperes peak inrush, and be capable of providing normal operation with peak current draw of up to twelve amperes.